1. Field of the Invention
The present invention relates to a control system for opening or closing an opening-closing member and, more particularly, to a control system for opening or closing an opening-closing member so adapted as to detect an event that a foreign material is caught between or by the opening-closing member such as a power window.
2. Description of the Related Art
An automotive vehicle is often provided with an opening-closing member such as a power window, a sun roof or a canvas top, which is arranged to be opened or closed by manual operations with switches. If a foreign material would be caught between or by the opening-closing member when the opening-closing member is being closed, the opening-closing member cannot be closed tightly so that the vehicle may not get started. When such a foreign material would be caught by the opening-closing member, safety measures should be taken by opening the opening-closing member or generating an alarm. At this end, the event that the foreign material has been caught by the opening-closing member should be detected.
Japanese Patent Unexamined Publication Kokai No. 61-21,288 proposes the technique for detecting the event of catching a foreign material, which utilizes an operation for detecting the magnitude of an electric current applied to a motor for driving an opening-closing member and a contact switch operable upon contact. This technique can detect the event of catching the foreign material with high accuracy by utilizing a phenomenon that an electric current applied to the motor increases to an extremely high level if the opening-closing member would catch the foreign material. If the foreign material would be caught by the opening-closing member, the electric current applied to the motor becomes high upon occurrence of the event and a difference in the electric current becomes also high, compared with the event in which the opening-closing member is closed normally. Whether the foreign material is caught by the opening-closing member can be determined by detecting the difference in the electric current from the magnitude of electric current under normal circumstances.
In order to accurately detect the event that the foreign material has been caught by utilizing the contact switch, a number of contact switches are required resulting in an increase in costs. Further, positions in which the contact switches are disposed may exert a great influence upon the accuracy of detecting the event of catching the foreign material.